Offshore oil rigs are supported by work boats, supply boats, crew boats and helicopters. These logistical supply vehicles cost a lot to maintain. Using a barge as an intermediary storage/work platform can reduce the number of runs needed by these vehicles. One of the most prominent materials that requires daily logistical support is the drilling fluid associated with the oil or gas well being drilled by that rig.
Various fluids (“well fluids”) may be used on the oil rig and may include both solids and liquids. Common uses for well fluids include: lubrication and cooling of drill bit cutting surfaces while drilling generally or drilling-in (i.e., drilling in a targeted petroleum bearing formation), transportation of “cuttings” (pieces of formation dislodged by the cutting action of the teeth on a drill bit) to the surface, controlling formation fluid pressure to prevent blowouts, maintaining well stability, suspending solids in the well, minimizing fluid loss into and stabilizing the formation through which the well is being drilled, fracturing the formation in the vicinity of the well, displacing the fluid within the well with another fluid, cleaning the well, testing the well, placing a packer fluid, abandoning the well or preparing the well for abandonment, and otherwise treating the well or the formation.
Since environmental problems and logistics are difficult and space is a priority on an oil rig, the storage and handling of fluids must be done as efficiently as possible. These fluids include various components that may be recycled and re-used or may be treated prior to disposal. Between the various operations, these fluids may be temporarily stored in a tank system. For example, when a wellbore fluid brings cuttings to the surface, the mixture is typically subjected to various mechanical treatments (shakers, centrifuges, etc.) to separate the cuttings from the recyclable wellbore fluid. However, the cuttings may need to be treated or the recyclable wellbore fluid may need to be stored until it is used again. Oil rig pit systems are currently very limited and cannot process the mud mix.
Typically, storage vessels are provided on a lower level of the platform and gravity is used to provide the fluids to them. Environmental controls no longer allow washing out storage pits through the dump valves into the ocean. These residues left in an open pit mud mix carrier can be extremely difficult to displace resulting in huge vessel tank cleaning costs in port. All solvents and water used to clean the inside of the pit are also deemed hazardous and require processing as well.
These limitations and costs complicate the transportation of fluid back to land for additional processing and treatment. Furthermore, as disclosed below, this additional treatment can be mounted on a barge. This obviates the need for any transportation back to shore. Accordingly, there exists a need for a drill fluids tank system to be incorporated into a barge design or placed upon a barge which will moor alongside or in close proximity to an operational well.
Referring to FIG. 1, the drawing illustrates a conventional double-hulled barge design 1 which has a main deck that is flat. With a conventional design most fluids are stored within the barge hull 2 and cargo/equipment is mounted onto the main deck. Both fluid and cargo can be in transit or in operations while on the barge.
Conventional barge designs require a double hull when storing any hazardous fluid within its hold that is greater than 600 cubic meters in volume. This is in accordance with International Maritime Organization (IMO) regulations on transporting hazardous fluids. However, constructing a double hull over the entire ship to comply with these regulations is very expensive.
Referring to FIG. 2, the storage of drilling fluids within the barge's tanks 4 creates several issues for the end user which the novel recessed design avoids. Drilling fluids are heavy, thick and burdened with solids both drilled solids and mixed chemical solids. These solids settle out quickly if left unattended (not mixed or transferred). This hazardous fluid (drilling muds and/or base oils) can become most difficult to remove from a hold down deep in the barge. To remove this settled fluid from any barge pit/tank system within the tank 4 could require personnel to enter that confined space under the main deck 3 to work at removing the product.